Currently, when wearing an earphone, such as an Active Noise Cancellation (ANC) earphone, the user hears low environmental noises due to the strong noise cancellation function of the ANC earphone, and thus the user is not so sensitive to alert sounds (e.g., automobile horn honking) in the external environment, and alerts are identified more visually. However, if the wearer is quickly walking, running or violently acting, his ability to visually identify alerts is weakened, which may bring dangers to the wearer.